1. User uses SAP GUI to perform a transaction.
2. User request is handled by the dispatcher.
3. Dispatcher keeps the request in Queue
4. Based on available resources a process is allocated to user requests based on FIFO.
5. WP task handler interpret the user request.
6. Check the content is available in R/3 buffers.
7. Communicate with Oracle Client to communicate with DB in native language.
8. R/3 Work process handovers the task to database shadow process (1:1 Ratio between R3WP: DBWP)
9. DB Shadow process checks the task contains valid table and field definitions. IF the table/ Field definition does not exists gets a copy from the database and update the DB Cache/ LIB Cache.
10. DB Shadow checks if any SQL Execution plan exists. If not it builds the plan based on cost based optimizer and update SQL Cache.
11. DB Shadow checks if the requested content exist in DB Buffer if not fetch the content from database and updates DB Buffer.
12. The response is handover to R/3 Work Process.
13. R/3 Work process checks if it is eligible for buffering then keeps a copy in R/3 buffers.
14. Response is sent to the user.
Refer init<SID>.ora file